Apple’s board of directors “is doing great disservice to shareholders by not having markedly increased its buyback,” Icahn tweeted.

Apple declined comment on Icahn’s tweets, referring Re/code to its latest proxy statement in which it recommends voting against Icahn’s advisory proposal asking it to increase the size of its stock buyback program in 2014 to $50 billion. Apple’s position: It already increased the size of its dividend and stock buyback program to $100 billion in 2013, and is thoughtfully considering options for returning additional cash to shareholders.

“In March 2012, the company announced a quarterly dividend and share repurchase program totaling $45 billion,” Apple said in its proxy. “In April 2013, the board authorized a dramatic increase, more than doubling the size of the program to $100 billion, raising the dividend, and increasing the share buyback authorization to $60 billion. As such, the company is one of the largest dividend payers in the world and has the largest share repurchase authorization in history. The company has executed aggressively against the capital return program, spending $23 billion of the $60-billion share repurchase authorization in fiscal 2013 alone.”